Cranberry has been shown useful in the prevention of urinary infection by E. coli. In this study, we examined the changes in the hydrophobicity of P fimbriated E. coli and biofilm formation after incubation with commercial cranberry syrup extract at various concentrations. After incubating a bacterial suspension with cranberry at dilutions of 1:100 and 1:1000, tests of haemagglutination inhibition, surface hydrophobicity and biofilm formation were carried out. The surface hydrophobicity of E. coli decreased significantly after incubation with cranberry and this effect was not modified by the culture medium. Biofilm formation was inhibited after incubation with cranberry syrup and this effect was dependent on the culture medium. Thus, in some circumstances cranberry can modify nonspecific adhesive properties of E. coli. In previous studies, cranberry has only been implicated in the inhibition of P-fimbriated E. coli, but our observations show that it acts by modifying adhesive properties under P-related fimbriae.